Apple source code for a core component of iPhone's operating system has purportedly been leaked on GitHub, that could allow hackers and researchers to discover currently unknown zero-day vulnerabilities to develop persistent malware and iPhone jailbreaks.

The source code appears to be for iBoot—the critical part of the iOS operating system that's responsible for all security checks and ensures a trusted version of iOS is loaded.

In other words, it's like the BIOS of an iPhone which makes sure that the kernel and other system files being booted whenever you turn on your iPhone are adequately signed by Apple and are not modified anyhow.

The iBoot code was initially shared online several months back on Reddit, but it just resurfaced today on GitHub (repository now unavailable due to DMCA takedown). Motherboard consulted some security experts who have confirmed the legitimacy of the code.

However, at this moment, it is unclear if the iBoot source code is completely authentic, who is behind this significant leak, and how the leaker managed to get his/her hands on the code in the first place.

The leaked iBoot code appears to be from a version of iOS 9, which signifies that the code is not entirely relevant to the latest iOS 11.2.5 operating system, but some parts of the code from iOS 9 are likely still used by Apple in iOS 11.

"This is the SRC for 9.x. Even though you can’t compile it due to missing files, you can mess with the source code and find vulnerabilities as a security researcher. It also contains the bootrom source code for certain devices…," a security expert said on Twitter.

The leaked source code is being cited as "the biggest leak in history" by Jonathan Levin, the author of a number of books on iOS and macOS internals. He says the leaked code seems to be the real iBoot code as it matches with the code he reverse-engineered himself.

Apple has open sourced some portions of macOS and iOS in recent years, but the iBoot code has been carefully kept private.

As Motherboard points out, the company treats iBoot as integral to the iOS security system and classifies secure boot components as a top-tier vulnerability in its bug bounty program, offering $200,000 for each reported vulnerability.

Therefore, the leaked iBoot code can pose a serious security risk, allowing hackers and security researchers to dig into the code to hunt for undisclosed vulnerabilities and write persistent malware exploits like rootkits and bootkits.

Moreover, jailbreakers could find something useful from the iBoot source code to jailbreak iOS and come up with a tethered jailbreak for iOS 11.2 and later.

It is worth noting that newer iPhones and other iOS devices ship with Secure Enclave, which protects against some of the potential issues that come with the leaked iBoot source code. So, I really doubt that the leaked code will be of much help.

Apple has yet to comment on the recent leak, though Github has already disabled the repository that was hosting the iBoot code after the company issued a DMCA takedown notice. However, the code is already out there.